(a) Field of the Invention
This invention relates to a textile material for use as the outer shell of a firefighter garment. More particularly, the invention is concerned with the material of the outer shell of a firefighter garment that increases the mobility and comfort of the wearer and, overcomes the problem of decreasing mechanical resistance as fabric weight reduces.
(b) Description of Prior Art
All fabrics used in the manufacture of protective clothing for firefighters must satisfy minimum performance requirements for flame, heat and tear resistance, as well as for thermal protection in general.
The clothing is normally made of a composite layer of materials including an outer shell which is most often constructed of spun yarns. These spun yarn materials do not slide easily on themselves or on surfaces inside or outside (e.g. other layers of the garment) with which they come into contact. As a result, a certain amount of body energy is required to move in the garments or flex joints, and to otherwise perform functions associated with the job of the wearer.
In the design of an outer shell, care must be taken not to fall below the minimum performance requirements of the various national standards. For example, a garment could be made lighter by simply employing lighter weight outer shell fabrics, however, as fabric weight drops, so does its mechanical resistance.
One method for overcoming the decrease in mechanical resistance as fabric weight decreases is to use filament instead of spun yarns, the former having very high tensile and abrasion strength. Similarly, filament yarns are more slippery than spun yarns thereby reducing friction between the filament fabric and any other fabric with which it may come in contact. This slipperiness increases the flexibility and mobility of the garment thereby reducing metabolic heat build-up.
However, filament fabrics often have problems as a result of the filament type or the fabric weave:
plain weave filament fabrics often suffer from seam slippage;
100% NOMEX.RTM. filament fabrics experience break-open before spun NOMEX.RTM./KEVLAR.RTM. blends;
100% KEVLAR.RTM. filament is vulnerable to UV. degradation and to fibrillation.
One of the leading causes of firefighter injury and mortality is stress. Stress may be caused by metabolic heat build-up and retention which in turn may be partly caused by the weight of the garment, the insulation properties of the garment, or the impediments to movement that the garment may present. Even if circumstances are not severe enough to make heat stress a threat, wearer comfort is decreased if the garment is heavy and constricting.
U.S. Pat. No. 4,583,247 describes a heat insulating garment made of a composite interlining sheet of porous material having low heat conductivity and high resilience. A layer of flexible reflective material is bonded to the outside of the porous material.
U.S. Pat. No. 4,897,886 describes a firefighter's garment having an outer layer, an intermediate layer, and an inner layer. Spacer elements are disposed between two of the layers of the garment to provide air spaces between layers of the garment. This design seeks to enhance thermal protective performance without significantly increasing garment weight. Its primary objectives are not:
reduction in garment weight
nor enhanced mobility
nor equal or superior heat and mechanical resistance at lower fabric weights.
U.S. Pat. No. 4,892,757 relates to fire block textile material including a carrier means and a textile to provide cover in a first state and a fire block or barrier in a second state.
U.S. Pat. No. 4,922,522 describes a design which seeks to increase flexibility at certain places in the garment by reducing the fabric thickness in these specific areas. Coincidentally, this would provide a very small reduction in garment weight.
U.S. Pat. No. 5,001,781 seeks to increase thermal protection and hence weight and thickness in only selected areas of the garment.
U.S. Pat. No. 5,136,723 discloses a firefighter garment including an outer shell, a moisture barrier within the shell and an inner thermal barrier. The outer shell may be made of NOMEX.RTM. or KEVLAR.RTM. fibers. The moisture barrier may be made of NOMEX.RTM. fibers and the thermal barrier may have a face cloth of NOMEX.RTM. or KEVLAR.RTM.. The aim of this Patent is the promotion of moisture vapor (perspiration) transmission from the inside to the outside of the garment without sacrificing thermal protective performance.
It is object of the present invention to provide a textile material for the outer shell of a firefighter garment that increases wearer comfort, reduces metabolic energy requirements and decreases metabolic heat build-up.
It is another object of the present invention to reduce the overall weight of the garment without compromising the mechanical resistance of the layers of the fabric.
It is another object of the present invention to provide an outer shell for firefighter garments that reduces the coefficients of static and sliding friction between the layers of the garment and between the garment and other interior or exterior surfaces which it may contact.
It is another object of the present invention to reduce the bulk of material at flex points of a firefighter garment such as at the elbows, shoulders, knees, underarms, and hence reduce mechanical resistance to body movement.